Ms.King, I'm afraid that you can't stay in Hong Kong for 2 years without working. The Dependant Visa of HK is issued to the lineal relatives of a person who is a holder of an employment visa (except foreign domestic helpers and imported workers), or a student visa of HK. However, you are just his girlfriend, there is no marriage license, so you can't apply for this kind of visa. Then you can't stay in HK for such a long time.

UK Citizens are exempt from visa to Hong Kong for up to 180 days, so you can stay in HK for half a year, then return to UK, and go to Hk again for another 6 months.

i am in the same position, I was wondering if you coulf offer some advice on ways that i could stay out there for longer than six months and also ways in which i could earn money. I hear that many people go out to hong kong to teach english but was also wondering as I am into the arts and media whether any hong kong can offer any job opportunities in this area... and where to look?? I am also a BA

You are right that you can stay in Hk for longer than 6 months if you apply for a Hk Employment visa, but you have to have a job in HK firstly.
You can search the job offers of Hk on ther internet, But I'm afraif it is difficult to find a job in Hk, since the personnel market of Hk is much too crowded